Welcome to the next exciting part of our Redis-based backend system project. In this unit, we will focus on building leaderboard functionality using Redis's sorted sets with PHP. Building a leaderboard is a popular use case for many applications, such as games and competitive platforms. You’ve got a good handle on managing user data from previous lessons, so let’s build on that foundation.

Let's briefly review what we’ll focus on in this unit. Our main tasks will be:

1. Adding user scores to a leaderboard: We will store user scores using Redis sorted sets.
2. Retrieving the leaderboard: We will fetch and display the top users and their scores.
3. Getting a user's rank and score: We will retrieve the ranking and score of a specific user.

Below are some key parts of the code you will be working with to perform these tasks.

This example demonstrates how to add a score for a user, retrieve the top scores, and fetch a user’s rank and score using PHP. You are familiar with the zadd and zrevrange commands from previous lessons. These commands are used to add scores and retrieve the leaderboard, respectively.